With the aging of the population there has occurred an increase in the incidences of degenerative diseases of the spine and this trend is expected to continue with the continuing increase in the percentage of elderly people in the population. Spinal stenosis is one of the most frequent forms of spinal degenerative disease observed. One conventional treatment of spinal stenosis has been laminectomy and decompression of compressed vertebrae and additionally fusing the treated vertebrae if instability exists. Many potentially negative side effects are inherent in this form of treatment, including profuse bleeding, substantial risk of infection, potential nerve damage sometimes leading to paralysis and/or bladder/bowel dysfunction, dural tears, persistent fluid leakage, arachnoiditis, continuing chronic pain, non-union (if fusion is performed), fusion hardware failure, donor site pain, adjacent segment disease, long operation times, and substantial operation costs.
Additionally, there are the inherent general risks of the surgical procedure and the medical risks including, but not limited to: bleeding, infection, nerve or vessel damage, risks of anesthesia, death, need for further surgery, iatrogenic instability, epidural hematoma, failure of implants and/or associated hardware, misplacement of implants and hardware, migration of implants and hardware, heart attack, stroke, deep venous thrombosis, pulmonary embolism, spinal cord and nerve damage, reflex sympathetic dystrophy, sexual dysfunction, positioning problems, brachial plexus injuries, traction injuries, swallowing difficulties, problems with vocal cords, airway obstruction, postoperative swelling, need for prolonged intubation, persistent dural fistula, paralysis, blindness, no relief of current symptoms, possible development of new symptoms, possible worsening of current symptoms, possible need for intraoperative change of procedure, possible need for fusion of the spine as determined intraoperatively, and other rare risks not named above.
Other types of implants have been developed to distract the spinous processes without the performance of laminectomy or fusion to increase the space for existing nerves to thereby relieve pain. Implantation of these implants typically require a large incision and dissection on both sides of the spinous processes. Multiple steps of dilation and distraction are performed prior to implantation of the implant in order to finally provide a sufficient interspinous space to wedge the implant between the spinous processes. Examples of implants of these types are described in U.S. Pat. Nos. 5,496,318; 5,645,599; 5,928,232; 6,149,652; 6,514,256; 6,695,842; and 6,761,720. Further, many of these devices are rigid, inflexible and/or non-adjustable wedge-like implants that require dissection of muscle tissue and/or ligaments such as the supraspinous ligament and interspinous ligament.
Other attempts have been made at providing a dynamic stabilization device, but these attempts have generally required attachment to the pedicles, which typically not only have the drawbacks associated therewith as noted above (large, bilateral incisions, etc.), but also, these types of implants compromise revision strategies when they fail. The attachment of pedicle-based dynamic stabilization can result in loosening of one or more of the pedicle screws used to attach the stabilizer to the pedicles, which can result in failure of fixation. This can preclude the salvage of pedicle screws for revision surgery and thus require more aggressive surgery. Other complications that can result from pedicle-based dynamic stabilizer arrangements include, but are not limited to: debris resulting from wear, and/or cut-out of pedicle screws into the spinal canal, which can result in neurological deterioration.
In view of these and other drawbacks with using currently existing spine treatments and inter-spinous implants, there is a continuing need for improved procedures and implants to treat disorders of the spine and pain associated therewith, and particularly for treatment of degenerative spine disorders, in the elderly as well as in any other vertebrate patients. It would be further advantageous to provide implants that are implantable via minimally invasive procedures, to reduce trauma, risks of infection and costs relative to those associated with currently available procedures. Still further, it would be desirable to provide such implants to be removable (i.e., explanted), if desired, by minimally invasive procedures. The ability to adjust the amount of distraction between the spinous processes, both during initial implantation and at a later time after completion of the implantation procedure, would also be desirable. It would also be desirable to provide devices that have the above advantages and also provide dynamic stability. It would be further desirable to provide devices that can optionally be used in a fusion procedure.